Booster pump fob aircraft fuel



Ap 1945- R. R. CURTI$ Rfi 22,739

BOOSTER PUMP FOR AIRCRAFT FUEL SYSTEMS Original Filed Aug. 10, 1940 2 Sheets-Sheet 1 IQUJGELL )9. Cup TM Ap 2, 1946. R. RfCURTlS BOOSTER PUMP FOR AIRCRAFT 'FUEL SYS TEMS Original Filgd Aug. 10, 1940 2 Sheets-Sheet 2 Pusssu. CUPT/J Reissued Apr. 2, 1946 Re; 223a BOOSTER PUMP FOR AIRCRAFT FUEL SYSTEMS Russell E. Curtis, Dayton,

Pump C mp n D y n.

Original No.

rial No. 352,064,

Ohio, assignor to Curt Ohio, a corporation of 2,292,993, dated August 11,1942, -Se- August 10, 1940. Application for reissue June 14,1944, Serial No. 540,232

11 Claims. (Cl. 103-113) This invention relates to high altitude fuel systems for aircraft and particularly to a booster pump for use in connection therewith.

In the operation of aircraft with gasoline as the fuel, it is well known that, as the atmospheric pressure drops with increase in altitude, a point is flnallyreached where air and fixed gases in solution start to evolve and lighter constituents in the fuel to vaporize, until the engine fuel pump is no longer capable of delivering fuel in a. fully liquid form to the engine. This condition frequently gives rise to what is known in the art as "vapor lock." The agitation of the fuel by the engine pump serves to aggravate the dimcu lties that may be experienced by accelerating, the separation of the air, or other fixed gases, or vapors from the liquid fuel.

Where, as is usual in aircraft design, the fuel tank is considerably. below the level of the engine and its carburetor, the pressure at the inlet side of the engine fuel pump drop still lower than the atmospheric pressure on the fuel in the tank, due to the suction head at the engine pump inlet.

Even where the amount of elevation of the engine above the fuel tank is of little consequence, the suction line is usually of considerable length and, due to weight restrictions, of small diameter, so that a considerable equivalent suction head is created at the inlet side of the'engin'e pump.

The result of the foregoing conditions is that the fuel starts breaking into vapor at the engine pump inlet at considerably lower altitude than it does in the fuel tank, and much inventive eifort has been expended, in attempts to overcome this difflculty.

In the specificationof my copending application, Serial No. 324,658, filed March 18, 1940, it is proposed to employ a booster pump, placed anywhere below the hydraulic gradient in the 'suctlon line, with means to bring it into action to raise the pressure in the suction line before an altitude has been reached where the fuel would ordinarily boil at the engine pump inlet.

But while this addition of a booster pump arrangement to the fuel system, materially increases the altitude range, by boosting the pressure at the suction inlet of the engine pump where the pressure'drop is greatest,- so that the e gine pump may deliver unbroken liquid, fuel to the engine, it is obvious that, if the craft is taken to still higher altitudes, a P int will ulti-- mately be reached where the fuel will start breaking up in the fuel tank itself, and the booster pump will have diiiiculty in drawing fully liqueiied fuel from the tank for delivery into the suction line of the engine pump.

It is therefore an object of this invention to further increase the altitude range of aircraft, by

so designing the booster pump and so arranging it with respect to the fuel tank, that fully liquid fuel may be drawn from the tank considerably above the altitude at which the fuel has begun boiling in the tank. I

Other objects and advantages will become evident as the invention is further described with reference to the drawings, wherein,

Fig. 1 is an elevational view, partly in vertical section, of a booster pump and motor with a fragmentary portion of the fuel tank, all constructed and arranged in accordance with this invention. I

Fig. 2 is'a top plan view of the'booster pump unit removed from the tank. I

Fig.3 is a variant form of the arrangement of the booster pump with the tank.

Like numerals refer to like parts throughout the drawings. I v

The booster pump is of the centrifugal type comprising a pump casing Ill, provided internal- 1y with a volute I! which does not differ ly from those of common practice. A throat member H covers the open side of the volute and is held to the casing by the screws l6. g

The impeller comprises a hub 20, a flange 22 and a series of curved vanes 21. The impelleris secured to the motor shaft 28 by the key 28 and nut 30. v

As illustrated in Fig. 1, a mounting ring 32 is secured to the inside of the, lower wall of the tank ring 32 is 33, preferably by welding or similar means. The

blind tapped at circumferentially spaced intervals for the screws 34 which extend through the flange 38 of the pump casing and secure the pump to the tank. A gasket 38 between the flange and-tank seals against leakage.

The electric motor 40, which operates the pump, is substantially conventional, having a field ring 42 held between heads 44 and 48 by nuts II. The upper head It is an integral portion of the pump casing l0 and contains a seal. not shown.

to prevent leakage from the pump into the motor. One of the drain plugs 5|. most convenient- .ly located for a particular installation, may be removed and a drain pipe inserted to dispose of any leakage which may occur.

Thusfar the centrifugal pump described does not differ materially from the conventional, but certain parts now, to be described are particumaterialends of the vanes 24,

, taper of the beveled edges 54 7 down through the larly designed and positionedwith respect to the tank to achieve a novel result.

In common practice, the diameter of the throat 52 of the member II is usually made the same as the diameter of the circle representing the inner but in the pump herein shown the circle defined by the constricted opening of the throat 52 overlies the vanes about midway of their lengths. Otherwise expressed, the circle defined by the throat opening is concentric with and lies intermediate the circlesdefined by the inner and outer tively.

ends of the vanes, respec- The inner halves of the vanes 24 which are exposed when viewed from above, as in Fig. 2. through the throat 52, are beveled on as at 54, Figs. 1 and 3, and the throat itself flares upwardly as at 58, the upper end of the flared part being substantially flush with the inside of the tank;

The convergency of the throat wall 58 and the of the vanes form approximate continuations of each other.

The result of this special structure and arrangement is that there is created, immediately above the throat, a funnel-shaped whirlpool of the fuel, the particles of which rotate in the same direction as the impeller and move in corkscrew fashion toward it. This whirlpool extends well upward into the tank and is present as soon as the booster pump is put into operation.

When an altitude is reached where the fuel in the tank starts breaking up, scattered bubbles 58 will first appear throughout the tank. However, as the fuel and bubble mixture approaches the impeller, the bubble are thrown outwardly along the tapered surface 56 of the throat member 52 and flow upwardly in the tank as indicated by the arrows in a path shown at ill. Upon approaching the surface of the fuel in the tank the bubble path widens out and the bubbles become larger until they burst at the surface of the fuel. The fuel is thus freed from the air and gases and drculates as indicated by the arrows down through the whirlpool as a substantially solid or fully liquid feed 62 to the impeller.

As a result a countercurrent circulation oi fuel and bubbles is created in the tank with the bubbles the whirlpool and with fully liquid fuelbeing fed impeller. The fully liquid fuel isthen thrown by funnel-shaped whirlpool to the In some instances, space limitations are such the bottom of the tank as in Fig. 1, and in such cases, the pump may be mountedas in Fig. 3, on a normally vertical end wall of the tank, by providing a sump 64 with an opening in the end wall near the bottom of the sump. The whirlpool 52 and its vortex lill will, in thi case, have a somewhat curved axis, but it has been found that separation of the vapor from the solid fuel will be almost as effective in this case as in that previously described.

The pump unit is the same inboth embodiments, only its position relative to the tank is different. It should be noted, however, that in both cases, the throat of the pump is comparatively shallow and opens directly into a large mass of fuel in the tank, thus lending itself to the centrifugal separation of the bubbles of gas or vapor from the'mass of liquid fuel with minaration of dissolved air and fixed gases and vapor before these gases can be entrapped and passed through the pump. To accomplish this I have found it necessary to greatly reduce the throat velocity over that which is normally rovided for, by increasing the inlet throat diameter and bevelling it outwardly toward the tank. As no advantage is taken of the velocity of incoming fluid, and as an abrupt change in velocity takes place as fluid reaches the impeller, efliciency is considerab y lowered.

Tobuild up a greater vortex requires the exv penditure of additional energy but increased agirising through the fuel outwardly from centrifugal force between the vanes on the impeller and the throat maining bubbles are forced from the fuel'outwardly along the path indicated at 80.

From the foregoing description it. will be seen that, equipped with a booster pump 01' the character disclosed, aircraft may be flown to considerably higher altitudes than has heretofore been, possible, for the reason that even after considerable vaporization is takin place in the fuel tank,

evidenced by bubbles 1 of 'vapor appearing throughout the mass, these bubbles may be separated out,'and fuel in a fully liquid state put under pressure in the suction line of the engine pump. r

If the throat of the booster pump were of conventional design, or if the pump were spaced further from the tank and fuel were conveyed to the vanes through a conduitiof some considerable length and of unvarying diameter, or if the vane throa proportions were conventional, vapor bubble appearing in the fuel would be trapped toth'e engine pump suction line in ever quantities until vapor lock occurred.

member where the last retake place in the suction tation is vital to successful altitude performance of this system. So the impeller vanes have been extended in toward the center of the impeller The booster the inlet, due to agitation of the liquid, and elsewhere in the tank; and the second to exert pressure on the engine pump suction line and prevent a further evolution of gas which might otherwise inlet line. or in the en- Sine Pump as the fuel is further agitated.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and itis, therefore, not the purpose to limit the wise than necessitated by the scope of the appended claims. 7

I claim as my invention: v

1. In a booster pump of the character described, a pump casing, an impeller, vanes on and radiating outwardly from the rotating axis of said impeller, and a member having a shallow conical inlet throat concentric with the axis of said impeller and tapered toward and adjacent one side of said vanes, the small end of said throat being of a diameter eters of the inner and outer ends of the vanes, and said vanes being beveled from the throat diameter inward. whereby the taper of the throat and the bevel of the vanes are substantial continuations of each other. I

patent granted hereon other-- substantially midway of the diamaavso on and comprising, a pump casing. an impeller, tapered vanes on said impeller,- and a flared throat member having one end adiacent said vanes, and its other ends in contact with the fuel in said tank, said throat having a diameter on the vane side substantially midway of the diameters of the inner and outer ends of the vanes, but flaring to a larger diameter on the tank side, the flare of the throat and the taper oi the vanes being substantial continuations of each other. l

3. in a fuel system for aircraft, a fuel tank, a centrifugal pump secured to the outside of said tank, said pump comprising, a pump casing, an impeller, vanes on said throat member having one side facing said vanes and the other side facing the fuel in said tank,

the throat in said member having a diameter on the vane side substantially midway of the in'side and outside diameters of the vanes, but flaring to a larger diameter on the tank side, and said vanes being tapered from the point adjacent the throat diameter to their inner ends, whereby said vanes are narrower at the inner ends.

4. A booster pump for attachment to a fuel tank, said pump comprising an impeller having vanes extending outwardly from the axis of said impeller, ,said vanes terminating at their inner and outer ends on circles concentric with and spaced from said axis to provide fluid flow passages therebetween having open inner and outer ends, and a member overlying said impeller on the tankside in closely spaced relation to the vanes and having a shallow inlet throat -converging toward said impeller to define a circular opening of a diameter intermediate those of said concentric circles and large enough to expose an appreciable length of the vanes effective for heating out bubbles of gas or vapor from the fuel.

5. A booster pump for attachment to an underside of a fuel tank, said pump comprising an impeller disc having radially extending vanes on the inlet face of said disc, said vanes being tapered at their inner ends toward said disc face and with their inner and outer ends lying in circles concentric with the disc axis, and a plate overlying said impeller on the tank side with its lower face in closely spaced relation to said vanes and having a shallow throat converging toward said impeller to define a circular opening of a diameter intermediate the diameters of said circles.

6. A booster pump for attachment to an underside of a fuel tank, said pump comprising an impeller disc having radially extending vanes 'on the inlet face of said disc, said vanes being tapered at their inner ends toward said disc face and with theirinner and'outer ends lying in circles concentric with the disc axis, and a plate overlying said impeller on the tank side with its lower face in closely spaced relation to said vanes and having a shallow throat converging toward said impeller to define a circular opening of a diameter intermediate the diameters of said circles, the convergency of said throat and the taper of said vanes being approximately continuations of each other.

'7. In combination with a lower or side wall of a fuel tank, a, booster pump comprising a casing secured to said wall and about an opening formed therein, --its axis perpendicular to said wall, said impeller having a circular flange with upstanding ribs impeller, and a shallow.

a driven impeller mounted with-- the liquid becomes 'saidtanktowardsaidaidstodeflneanopening of substantially greater diameter than the cir.- I

cle deiinedby the inner ends of said ribs.

8. ,A pump and motor unit comprising a motor, a casing therearound having an open mouthed outwardly flanged head portion defining a pump volute chamber and a central eway,a motor shaft extending from the motor through said passal way, a pump impeller on said shaft are ranged to impel fluid in the open mouth of said head portion into the ring in the mouth of the head portion overlying the volute chamber and defining an inlet to the impeller, and said flange of the head portion adapted to be attached to the wall of a-tank to flexedly connect the entire unit to a tank.

9. A device for separating gases and vapors from liquid such as volatile fuel and for pres suring fully liquid material which comprises a pump and motor unit having mounting means for attachment to a tank wall, a pump portion having a peripheral pumping inlet for communicatin directly with the interior of a tank, and an impleller adjacent the inlet having vanes communicating directly with said pumping 'chamber'for pumping liquid from the inlet to the chamber and for agitating the liquid, said vanes for agitating creating a stream of bubble-rich liquid in the tank flowing away fromthe inlet. I

10. In combination with a tank for liquid, a pump secured to said tank having an inlet communicating directly with the interior of the tank for receiving liquid directly therefrom, an impeller assembly in said pump having pumping vanes and agitating vanes, said agitating vanes acting on liquid ,entering the pump inlet before trapped in the pump and being in open unrestricted communication with the interior bf the tank to create in the liquid in the tank a stream of bubbles flowing away from the inlet, and said pumping vanes being eflective for pressuring bubble-freed liquid out of the tank.

11. A device for discharging fully liquid material such as volatile fuel or the like from a pond of the liquid in a container which comprises a pump casing arranged for direct connection to a wall of a container, said pump casing defining a pumping chamber having a shallow relatively large inlet throat diverging outwardly for direct unrestricted communication with the pond of liquid eller in said casing having umping vane portions underlapping said throat in close running clearance relation therewith together with agitating portions of appreciable length fully exposed to liquid in the pond and eifective for throwing outwardly into the pond along the diverging throat and away from the pumping vanes bubbles which are entrained in the liquid flowing to the pumping vanes.

12. In a fuel system, a fuel tank, a booster pump Q casing directly mountedon a wall of the tank and having a relatively large inlet threat in full unrestricted communication with fuel in the tank, a flat disk'impeller in said pump casing, upstanding pumping vanes on said impeller underlapping said throat in close running clearance relation therewith and defining open ended fluid flow passages, agitating vanes on of appreciable length in exposed uncovered relavolute chamber, a throat chamber and a central in the container, a centrifugal pump irnsaid impeller tion with the inlet of said throat in full unrestricted communication with the fuel in the tank, and said agitating vanes being effective for creating a stream of bubble-rich fuel in the tank flowing away from the inlet of said throat whereby said pumping vanes will discharge fully liquid fuel freed from bubbles.

13. In a fuel system for aircraft, a 'fuel tank, a centrifugal pump and motor unit directly secured to a wall of said tank, said pump comprising a pump casing, an impeller in said casing, vanes on said impeller, and a shallow throat member having one side closely adjacent to and overlapping portions of said vanes and the other side exposed to fuel in the tank, the throat in said throat member having'a diameter on the vane side intermediate the inside and outside diameters of the vanes but flaring to a larger diameter on the tank side, said vanes being beveled from a point intermediate their ends inwardly, and said beveled portions of the vanes being uncovered in said throat of the throat member in direct communication with fuel in the tank to agitate the fuel and create a stream of bubble rich fuel flowing upwardly in the tank away from the throat.

14. A device for discharging fully liquid material,*such as volatile fuel, from a source of liquid material, which comprises a pump having a portion defining a relatively large inlet throat communicating directly with said source, an impeller assembly adjacent said pump portion, vane portions on the impeller assembly underlapping said pump portion in closely spaced relation and defining walls of open-ended liquid flow pumping channels, and additional vane portions of appreciable length-on the impeller assembly in open liquid flow pumping channels, and additional vane portions of appreciable length on the impeller assembly in open unrestricted communication with the source of liquid and closely adjacent to and in communication with the inlet throat .in the path of liquid flow to the pumping channels/eflective for acting on the liquid material before it becomes confined in the channels to agitate the material and beat out therefrom bubbles of gas and vapor back to said source in countercurrent flow relation to liquid flowing to the inlet opening of the throat whereby said channels discharge fully liquid'material.

16. A device adapted for discharging fully liquid material, such as volatile fuel, from a source of liquid material, which comprises a pump having a pump chamber and a relatively large inlet throat communicating with said source, an impeller having vanes for pumping liquid from the inlet throat to the chamber, and for agitating the liquid, said vanes for pumping liquid defining walls of open-ended pumping channels having closed perimeters discharging into the pump unrestricted communication with the source of liquid and adjacent to and in communication with the inlet throat of said pump portion in the path ofv liquid fiow to the pumping channels efiective for acting on the liquid material before it becomes confined in the channels to agitate the material for releasing back to said source bubbles of gas and vapor and for creating in the source of liquid a bubble rich streamflowing in countercurrent relation to liquid flowing to the pump.

inlet.

15. A device for discharging fully liquid material, such as volatile gasoline, from a source of liquid material. which comprises a pump having a portion defining a relatively large inlet throat communicating with said source, an impeller assembly adjacent said pump portion including a disk spanning the inlet opening of the throat and underlapping said pump portion around the periphery thereof, vane portions on the outer peripheral portion of the disk underlapping said pump portion in closely spaced relation and defining with the disk and pump portion open-ended chamber, said inlet throat flaring outwardly on the inlet side thereof and being directed toward the peripheral portions of the vanes for agitating, said vanes for agitating having an appreciable length in open communication with the source of liquid and adjacent to and in communication with the relatively large inlet throat in the path of liquid fiow to the pumping channels and being eirectivefor acting on theliquid before it becomes confined in the pumping channels to beat out bubbles of gas and-vapor therefrom and form in said source a stream'of bubble rich liquid flowing away from the inlet throat.

17. A device for separating gases and vapors from liquid such as volatile fuel and for pressurin fully liquid material which comprises a pump and motor unit including a pump having a portion defining a large shallow inlet throat for communieating directly with a source of liquid, an impeller assembly adjacent said pump portion, vane portions on the impeller assembly underlapping said pump portion in closely spaced relation and defining 'walls pf open-ended liquid flow pumping channels, and additional vane portions of appreciable length on the impeller assembly exposed in unrestricted uncovered communication with the inlet side of said large shallow inlet throat in the path of liquid to the pumping channel and effective for acting on the liquid before it becomes confined in the pumping channels to beat out bubbles of gas and vapor therefrom and create in the liquid in advance of the inlet throat a stream of bubble rich liquid flowing .away from the inlet throat.

RUSSELL R. CURTIS. 

